Method and apparatus for allowing soft handoff of a CDMA reverse link utilizing an orthogonal channel structure

RELATED APPLICATION(S)

This application claims the benefit of U.S. Provisional Application No. 60/427,847, filed on Nov. 20, 2002 entitled “Component Technology Proposal for an Orthogonal Reverse Link”, and is a Continuation-in-Part of U.S. application Ser. No. 09/898,514, filed Jul. 3, 2001, now U.S. Pat. No. 7,006,428 entitled “Method for Allowing Multi-User Orthogonal and Non-Orthogonal Interoperability of Code Channels,” which claims priority to U.S. Provisional Application No. 60/219,789, filed Jul. 19, 2000 entitled “Method for Allowing Multi-User Orthogonal and Non-Orthogonal Interoperability of Code Channels on the Reverse Link of a CDMA System.” The entire teachings of the above applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The last twenty years have seen unprecedented growth in both the type and demand for wireless communication services. Wireless voice communication services, including cellular telephone, Personal Communication Services (PCS), and similar systems now provide nearly ubiquitous coverage. The infrastructure for such networks has been built-out to the point where most residents of the United States, Europe, and other industrialized regions of the world have not just one, but multiple service providers from which to choose.

Continued growth in the electronics and computer industries increasingly contributes to demand for access to the Internet and the myriad of services and features that it provides. This proliferation in the use of computing equipment, especially that of the portable variety, including laptop computers, handheld Personal Digital Assistants (PDAs), Internet-enabled cellular telephones and like devices, has resulted in a corresponding increase in the need for wireless data access.

While the cellular telephone and PCS networks are widely deployed, these systems were not originally intended for carrying data traffic. Instead, these networks were designed to efficiently support continuous analog signals as compared to the burst mode digital communication protocols needed for Internet communications. Consider also that voice communication is adequate with a communication channel bandwidth of approximately 3 kilohertz (kHz). However, it is generally accepted that for effective Internet communication, such as for Web browsing, a data rate of at least 56 kilobits per second (kbps) or higher is required.

In addition, the very nature of the data traffic itself is different from the nature of voice communication. Voice requires a continuous duplex connection; that is, the user at one end of a connection expects to be able to transmit and receive to the user at the other end of a connection continuously, while at the same time the user at the other end is also able to transmit and receive. However, access to Web pages over the Internet is, in general, very burst oriented. Typically, the user of a remote client computer specifies the address of computer files such as on a Web server. This request is then formatted as a relatively short data message, typically less than a 1000 bytes in length. The other end of the connection, such as at a Web server in the network, then replies with the requested data file which may be from 10 kilobytes to several megabytes of text, image, audio, or video data. Because of delays inherent in the Internet itself, users often expect delays of at least several seconds or more before the requested content begins to be delivered to them. And then once that content is delivered, the user may spend several seconds or even minutes reviewing, reading the contents of the page before specifying the next page to be downloaded.

Furthermore, voice networks were built to support high mobility usage; that is, extreme lengths were taken to support highway speed type mobility to maintain connections as the users of voice based cellular and PCS networks travel at high speeds along a highway. However, the typical user of a laptop computer is relatively stationary, such as sitting at a desk. Thus, the cell-to-cell high speed mobility considered critical for wireless voice networks is typically not required for supporting data access.

SUMMARY OF THE INVENTION

It would make sense to retrofit certain components of the existing wireless infrastructure to more efficiently accommodate wireless data. The additional functionality implemented for a new class of users who are high data rate but low mobility users should be backwards compatible with existing functionality for users who are low data rate, high mobility. This would permit using the same frequency allocation plans, base station antenna, build out sites, and other aspects of the existing voice network infrastructure to be used to provide the new high speed data service.

It would be particularly important to support as high a data rate as possible on the reverse link of such a network that is carrying data on the reverse link, e.g., from the remote unit to the base station. Consider that existing digital cellular standards such as the IS-95 Code Division Multiple Access (CDMA) specify the use of different code sequences in a forward link direction in order to maintain minimum interference between channels. Specifically, such a system employs orthogonal codes on the forward link, which defines individual logical channels. However, the optimum operation of such a system requires all such codes to be time aligned to a specific boundary to maintain orthogonality at the receiver. Therefore, the transmissions must be synchronized.

This is not a particular concern in a forward link direction since all transmissions originate at the same location, i.e., at a base transceiver station location. However, currently, digital cellular CDMA standards do not attempt to use or require orthogonality between channels in a reverse link direction. It is generally assumed that it is too difficult to synchronize transmissions originating from remote units located in different locations and at potentially quite different distances from the base station. Instead, these systems typically use a chip level scrambling code with unique shifts of this long pseudorandom code to distinguish the individual reverse link channels. Use of this scrambling, however, thus precludes the possibility of different users' transmissions being orthogonal to one another.

Accordingly, one embodiment of the present invention includes a system that supports communication among members of a first group of users and a second group of users. The first group of users, which may be legacy users of a digital Code Division Multiple Access (CDMA) cellular telephone system, encode their transmissions with a common first code. Such first group of users are uniquely identifiable by providing a unique code phase offset for each user. The second group of users, who may be users of a high speed data service, encode their transmissions using the same code and one of the code phase offsets of that code. However, each of the users of the second group further encode their transmissions with an additional code, the additional code being unique for each of the users of the second group. This permits the transmissions of the second group of users to be orthogonal to each other while still maintaining the appearance of collectively being a single user of the first group.

The code assigned to the first group of users may be a common chipping rate, pseudorandom code. The code assigned to the second group of terminals may typically be a set of unique orthogonal codes. The individual members of the first group of terminals may be distinguished by scrambling codes that have unique phase offsets of a selected longer pseudorandom noise sequence.

In a preferred embodiment, certain steps are taken to ensure proper operation of the signaling among the second group of users or so-called “heartbeat.” Specifically, a common code channel may be dedicated for use as a synchronization channel. This permits the maintenance of proper timing of the transmissions of the second group of terminals if, for example, the coding scheme is implemented in a reverse link direction.

In another embodiment, the users of the second group may be allocated specific time slots in which to transmit and therefore maintain the orthogonality through the use of time division multiple access. Again, the point is that the users of the second group collectively appear as a single user to the transmissions of the users in the first group.

The principles of the present invention allow current CDMA systems, designed for vehicular mobility, to support soft handoff for orthogonal channel users on their reverse link to increase the robustness of reverse link channel connections in a highly variable RF environment.

Since an orthogonal link must be time aligned to maintain orthogonality from one user to the next, a timing control loop is employed from a single base station. Orthogonality is not easily achieved to two base stations in a reverse link direction because the relative propagation time delays complicate time alignment at both base stations. Therefore, to use an orthogonal reverse link with soft handoff, there is a primary reverse link base station providing timing control and secondary base station(s) that may receive the transmissions non-orthogonally.

Specific criteria are defined to determine when it is advantageous to reassign the timing control from the primary base station to the secondary base station allowing for change of the orthogonal link from the first to the second base station. While there is only one orthogonal base station, signal levels received at the second base station may be sufficient for reception. These signals may be used to provide for diversity. This is particularly useful in high mobility systems.

Although only a single base station performs timing control, in a preferred embodiment, both perform power control. This is because, as the path loss to the non-orthogonal base station decreases as the user moves, the received power may become so strong it begins to generate excessive interference, reducing the capacity of the secondary base station. Therefore, when the signal level is adequate for reception at the secondary base station, commands or messages are transmitted to the subscriber unit to reduce the transmitted power. While these commands affect the received power at both the orthogonal base station and the non-orthogonal base station, it may be appropriate to reassign the timing control from the primary base station to the secondary base station. A typical condition may be when the measured path loss to the non-orthogonal or secondary base station exceeds some threshold difference of, for instance, 10 db.

Existing CDMA systems define reverse-link channelizations non-orthogonally. This is performed by defining unique spreading code shifts for each reverse-link user. Orthogonal and non-orthogonal backward compatibility can be achieved by orthogonal users for a primary base station sharing the same spreading code. When these user signals are received at other base stations, it is unlikely that they will be time aligned, but they will all have unique code shifts and be able to be uniquely identified based on the combination of code shift and orthogonal code. These signals are no more interfering than the standard non-orthogonal signals that are legacy to existing CDMA systems. Therefore, just as soft handoff is performed today, it can be performed with an orthogonal primary base station and non-orthogonal secondary base stations.

When the primary base station is re-assigned such that the timing now comes from a secondary base station (i.e., reverse link timing control handoff has taken place), there may be a significant delay and code phase offset. Using a conventional one-bit differential timing control loop may be too slow to quickly obtain orthogonality with the new base station when it is handed off. Therefore, when the handoff occurs, a gross timing adjustment command or message may be used to rapidly re-align the reverse link, where the gross timing adjustment may be absolute or relative. In the case of the timing command, the subscriber unit is told to make a coarse timing adjustment; in the case of the timing message, the subscriber unit autonomously responds to information in the timing message.

The criteria for timing control hand-off may be based on criteria, including at least one of the following:

1. The metric of an alternative path exceeds a threshold for a designated period of time;

2. The metric of an alternative path exceeds a threshold relative to the current path for a designated period of time;

3. The currently selected path drops below an absolute metric; or

4. The candidate path exceeds an absolute metric, where the metric may be one or more of the following <ul id="ul0001" list-style="none"><li id="ul0001-0001" num="0000"><ul id="ul0002" list-style="none"><li id="ul0002-0001" num="0025">a. Power;</li><li id="ul0002-0002" num="0026">b. SNR;</li><li id="ul0002-0003" num="0027">c. Variance of the power;</li><li id="ul0002-0004" num="0028">d. Variance of the SNR; or</li><li id="ul0002-0005" num="0029">e. Relative ratio of the above metrics between the two paths (i.e., the orthogonal link and the non-orthogonal link).</li></ul></li></ul>

Power control (or SNR control) of an orthogonal reverse link (RL) may be based on both orthogonal (aligned) and non-orthogonal paths. When the SNR of a non-orthogonal path meets a quality criterion as listed above while a power control loop is active, timing control of the subscriber unit may be re-assigned to the base station associated with the non-orthogonal path.

Referring to the power control loop, if a command is sent, rather than a message or report, the command may be the minimum of the SNR of each path. For example, if two paths are being tracked, and one needs power and the other has too much power, the power is commanded to be lessened. This applies to a soft hand-off function as well, where the power output by the subscriber unit is increased only if all commands or messages providing power metrics require it to be increased.

There may be a relative offset between commands from a non-orthogonal path of a base station and those of the orthogonal path. For instance, the commands requiring more or less power from non-orthogonal paths may need to be more consistent or for a longer period of time or for a longer duration before the orthogonal path is ignored and the other paths control the reduction in power. The intra base station orthogonal zone may be handled in a like manner, as above.

Power control may be maintained by both orthogonal and non-orthogonal base stations while timing orthogonality is controlled by one base station. While power control is being maintained to both the orthogonal and non-orthogonal base stations, commands or messages including metrics must be sent to the subscriber unit transmitter down the forward link.

The power control commands from each base station may be based upon whether a quality metric is achieved at each respective base station. This quality metric may be bit error rate, signal-to-noise ratio, received power, or Ec/Io. Provided the metric is satisfied, then a command to reduce transmission power is sent. Since the access terminal receives commands from both base stations, often it will receive conflicting commands. When this occurs, the access terminal obeys the command to power down if one exists. This is effectively an exclusive-OR function; for instance, a power-up occurs only if both base stations command power up. If either base station commands a power-down, then a power-down occurs at the access terminal. This holds true for multi-bit commands as well, where the minimum increase or the maximum decrease in power is obeyed.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.

<figref idref="DRAWINGS">FIG. 1</figref> is a block diagram of a wireless communications system supporting orthogonal and non-orthogonal links;

<figref idref="DRAWINGS">FIG. 2</figref> is a block diagram of a circuit employed by the access terminal of <figref idref="DRAWINGS">FIG. 1</figref>;

<figref idref="DRAWINGS">FIG. 3</figref> is a block diagram of the circuit of <figref idref="DRAWINGS">FIG. 2</figref> further including a code generator to operate on an orthogonal link with other access terminals;

<figref idref="DRAWINGS">FIG. 4</figref> is a block diagram of the wireless communications system of <figref idref="DRAWINGS">FIG. 1</figref> having multiple field units using orthogonal and non-orthogonal links;

<figref idref="DRAWINGS">FIG. 5</figref> is a block diagram of a base station processor (BSP) of <figref idref="DRAWINGS">FIG. 4</figref> having an orthogonal timing controller to control the timing of access terminals on the orthogonal link;

<figref idref="DRAWINGS">FIG. 6A</figref> is a network diagram of the network of <figref idref="DRAWINGS">FIG. 4</figref> having an alignment controller located in the base station processors;

<figref idref="DRAWINGS">FIG. 6B</figref> is a network diagram of the network of <figref idref="DRAWINGS">FIG. 4</figref> having an alignment controller located in the field unit;

<figref idref="DRAWINGS">FIG. 6C</figref> is a network diagram of the network of <figref idref="DRAWINGS">FIG. 4</figref> having an alignment controller located in a base station controller;

<figref idref="DRAWINGS">FIG. 7</figref> is a flow diagram of processes that may be employed by the base terminal station and access terminals of <figref idref="DRAWINGS">FIG. 4</figref> to make signals mutually orthogonal;

<figref idref="DRAWINGS">FIG. 8</figref> is a flow diagram of processes that may be employed by the base terminal stations and access terminal in the multi-cell environment of <figref idref="DRAWINGS">FIG. 4</figref> for soft-handoff; and

<figref idref="DRAWINGS">FIG. 9</figref> is a flow diagram of processes that may be employed by the base terminal stations and access terminals of <figref idref="DRAWINGS">FIG. 1</figref> for power control.

DETAILED DESCRIPTION OF THE INVENTION

A description of preferred embodiments of the invention follows.

<figref idref="DRAWINGS">FIG. 1</figref> is a block diagram of a Code Division Multiple Access (CDMA) communications system <b>10</b> that makes use of a signal encoding scheme in which a first class of logical channels are assigned unique long codes with different code phase offsets, and a second class of logical channels are provided by using a common code and common code phase offset, combined with an additional coding process using a unique orthogonal code for each channel.

In the following detailed description of a preferred embodiment, the communications system <b>10</b> is described such that the shared channel resource is a wireless or radio channel. However, it should be understood that the techniques described here can be applied to implement shared access to other types of media such as telephone connections, computer network connections, cable connections, and other physical media to which access is granted on a demand driven basis.

The system <b>10</b> supports wireless communication for a first group of users <b>110</b> as well as a second group of users <b>210</b>. The first group of users <b>110</b> are typically legacy users of cellular telephone equipment such as wireless handsets <b>113</b>-<b>1</b>, <b>113</b>-<b>2</b>, and/or cellular mobile telephones <b>113</b>-<i>h </i>installed in vehicles. This first group of users <b>110</b> principally use the network in a voice mode whereby their communications are encoded as continuous transmissions. In a preferred embodiment, these users' transmissions are forwarded from the subscriber units <b>113</b> through forward link <b>40</b> radio channels and reverse link <b>50</b> radio channels. Their signals are managed at a central location that includes a base station antenna <b>118</b>, base transceiver station (BTS) <b>120</b>, base station controller (BSC) <b>123</b>. The first group of users <b>110</b> are therefore typically engaged in voice conversations using the mobile subscriber units <b>113</b>, BTS <b>120</b>, and BSC <b>123</b> to connect telephone connections through the Public Switch Telephone Network (PSTN) <b>124</b>.

The forward link <b>40</b> in use by the first group of users may be encoded according to well known digital cellular standards such as this Code Division Multiple Access (CDMA) standard defined in IS-95B specified by the Telecommunications Industry Association (TIA). This forward link <b>40</b> includes at least a paging channel <b>141</b> and traffic channel <b>142</b>, as well as other logical channels <b>144</b>. These forward link <b>40</b> legacy channels <b>141</b>, <b>142</b>, <b>144</b> are defined in such a system by using orthogonally coded channels. These first group of users <b>110</b> also encode their transmissions over the reverse link <b>50</b> in accordance with the IS-95B standard. They therefore make use of several logical channels in a reverse link <b>50</b> direction, including an access channel <b>151</b>, traffic channel <b>152</b>, and other logical channels <b>154</b>. In this reverse link <b>50</b>, the first group of users <b>110</b> typically encode the signals with a common long code using different code phase offsets. The manner of encoding signals for the legacy users <b>110</b> on the reverse link <b>50</b> is also well known in the art.

The communications system <b>10</b> also includes a second group of users <b>210</b>. This second group of users <b>210</b> are typically users who require high speed wireless data services. Their system components include a number of remotely located Personal Computer (PC) devices <b>212</b>-<b>1</b>, <b>212</b>-<b>2</b>, . . . <b>212</b>-<i>h</i>, . . . <b>212</b>-<i>l</i>, corresponding remote Subscriber Access Units (SAUs) <b>214</b>-<b>1</b>, <b>214</b>-<b>2</b>, . . . <b>214</b>-<i>h</i>, . . . <b>214</b>-<i>l</i>, and associated antennas <b>216</b>-<b>1</b>, <b>216</b>-<b>2</b>, . . . <b>216</b>-<i>h</i>, . . . <b>216</b>-<i>l</i>. Centrally located equipment includes a base station antenna <b>218</b>, and a Base Station Processor (BSP) <b>220</b>. The BSP <b>220</b> provides connections to an from an Internet gateway <b>222</b>, which in turn provides access to a data network such as the Internet <b>224</b>, and network file server <b>230</b> connected to the network <b>222</b>.

The PCs <b>212</b> may transmit data to and receive data from network server <b>230</b> through bi-directional wireless connections implemented over the forward link <b>40</b> and reverse link <b>50</b> used by the legacy users <b>110</b>. It should be understood that in a point to multi-point multiple access wireless communication system <b>10</b> as shown, a given base station processor <b>220</b> supports communication with a number of different active subscriber access units <b>214</b> in a manner which is similar to a cellular telephone communication network.

In the present scenario, the radio frequencies allocated for use by the first group <b>110</b> are the same as those allocated for use by the second group <b>210</b>. The present invention is specifically concerned with how to permit a different encoding structure to be used by the second group <b>210</b> while creating minimal interference to the first group <b>110</b>.

The PCs <b>212</b> are typically laptop computers <b>212</b>-<i>l</i>, handheld units <b>212</b>-<i>h</i>, Internet-enabled cellular telephones or Personal Digital Assistant (PDA) type computing devices. The PCs <b>212</b> are each connected to a respective SAU <b>214</b> through a suitable wired connection such as an Ethernet-type connection.

An SAU <b>214</b> permits its associated PC <b>212</b> to be connected to the network file server <b>230</b> through the BSP <b>220</b>, gateway <b>222</b> and network <b>224</b>. In the reverse link direction, that is, for data traffic traveling from the PC <b>212</b> towards the server <b>230</b>, the PC <b>212</b> provides an Internet Protocol (IP) level packet to the SAU <b>214</b>. The SAU <b>214</b> then encapsulates the wired framing (i.e., Ethernet framing) with appropriate wireless connection framing and encoding. The appropriately formatted wireless data packet then travels over one of the radio channels that comprise the reverse link <b>50</b> through the antennas <b>216</b> and <b>218</b>. At the central base station location, the BSP <b>220</b> then extracts the radio link framing, reformatting the packet in IP form and forwards it through the Internet gateway <b>222</b>. The packet is then routed through any number and/or any type of TCP/IP networks, such as the Internet <b>224</b>, to its ultimate destination, such as the network file server <b>230</b>.

Data may also be transmitted from the network file server <b>230</b> to the PCs <b>212</b> in a forward link <b>40</b> direction. In this instance, an Internet Protocol (IP) packet originating at the file server <b>230</b> travels through the Internet <b>224</b> through the Internet gateway <b>222</b> arriving at the BSP <b>220</b>. Appropriate wireless protocol framing and encoding is then added to the IP packet. The packet then travels through the antenna <b>218</b> and <b>216</b> to the intended receiver SAU <b>214</b>. The receiving SAU <b>214</b> decodes the wireless packet formatting, and forwards the packet to the intended PC <b>212</b> which performs the IP layer processing.

A given PC <b>212</b> and the file server <b>230</b> can therefore be viewed as the end points of a duplex connection at the IP level. Once a connection is established, a user at the PC <b>212</b> may therefore transmit data to and receive data from the file server <b>230</b>.

From the perspective of the second group of users <b>210</b>, the reverse link <b>50</b> actually consists of a number of different types of logical and/or physical radio channels including an access channel <b>251</b>, multiple traffic channels <b>252</b>-<b>1</b>, . . . <b>252</b>-<i>t</i>, and a maintenance channel <b>53</b>. The reverse link access channel <b>251</b> is used by the SAUs <b>240</b> to send messages to the BSP <b>220</b> to request that traffic channels be granted to them. The assigned traffic channels <b>252</b> then carry payload data from the SAU <b>214</b> to the BSP <b>220</b>. It should be understood that a given IP layer connection may actually have more than one traffic channel <b>252</b> assigned to it. In addition, a maintenance channel <b>253</b> may carry information such as synchronization and power control messages to further support transmission of information over the reverse link <b>50</b>.

Similarly, the second group of users have a forward link <b>40</b> that includes a paging channel <b>241</b>, multiple traffic channels <b>242</b>-<b>1</b> . . . <b>242</b>-<i>t</i>, and maintenance channel <b>243</b>. The paging channel <b>241</b> is used by the BSP <b>220</b> to not only inform the SAU <b>214</b> that forward link traffic channels <b>252</b> have been allocated to it, but also to inform the SAU <b>214</b> of allocated traffic channels <b>252</b> in the reverse link direction. Traffic channels <b>242</b>-<b>1</b> . . . <b>242</b>-<i>t </i>on the forward link <b>40</b> are then used to carry payload data information from the BSP <b>220</b> to the SAUs <b>214</b>. Additionally, maintenance channels <b>243</b> carry synchronization and power control information on the forward link <b>40</b> from the base station processor <b>220</b> to the SAUs <b>214</b>. It should be understood that there are typically many more traffic channels <b>241</b> than paging channels <b>241</b> or maintenance channels <b>243</b>. In the preferred embodiment, the logical forward link channels <b>241</b>, <b>242</b>, and <b>243</b> and <b>251</b>, <b>252</b>, and <b>253</b> are defined by assigning each channel a pseudorandom noise (PN) channel code. The system <b>10</b> is therefore a so-called Code Division Multiple Access (CDMA) system in which multiple coded channels may use the same radio frequency (RF) channel. The logical or codes channels may also be further divided or assigned among multiple active SAUs <b>214</b>.

The sequence of signal processing operations is typically performed to encode the respective reverse link <b>50</b> logical channels <b>51</b>, <b>52</b>, and <b>53</b>. In the reverse link direction, the transmitter is one of the SAUs <b>214</b> and the receiver is the Base Station Processor (BSP) <b>220</b>. The preferred embodiment of the invention is implemented in an environment where legacy users of a CDMA digital cellular telephone system such as one operating in accordance with the IS-95B standard are also present on the reverse link <b>50</b>. In an IS-95B system, reverse link CDMA channel signals are identified by assigning non-orthogonal pseudorandom noise (PN) codes.

Turning attention now to <figref idref="DRAWINGS">FIG. 2</figref>, the channel encoding process for the first group of legacy users <b>110</b> will be described in greater detail. This first class of users includes, for example, digital CDMA cellular telephone system users that encode signals according to the IS-95B standard as mentioned above. The individual channels are therefore identified by modulating the input digitized voice signal by a pseudorandom noise (PN) code sequence for each channel. Specifically, the channel encoding process takes an input digital signal <b>302</b> that represents the information to be transmitted. A quadrature modulator <b>304</b> provides an in-phase (i) and quadrature (q) signal path to a pair of multipliers <b>306</b>-<i>i </i>and <b>306</b>-<i>q</i>. A short pseudorandom noise (PN) code generator <b>305</b> provides a short (in this case a 2 15 -1 or 32767 bit) length code used for spectrum spreading purposes. The short code typically therefore is the same code for each of the logical channels for the first group <b>110</b>.

A second code modulation step is applied to the (i) and (q) signal paths by multiplying the two signal paths with an additional long PN code. This is accomplished by the long code generator <b>307</b> and the long code multipliers <b>308</b>-<i>i </i>and <b>308</b>-<i>q</i>. The long code serves to uniquely identify each user on the reverse link <b>50</b>. The long code may be a very long code, which, for example, only repeats every 2 42 -1 bits. The long code is applied at the short code chipping rate, e.g., one bit of the long code is applied to each bit output by the short code modulation process, so that further spectrum spreading does not occur.

Individual users are identified by applying different phase offsets of the PN long code to each user.

It should be understood that other synchronization steps need not be taken for the first group of users <b>110</b>. Specifically, these transmissions on the reverse link <b>50</b> are designed to be asynchronous and therefore are not necessarily perfectly orthogonal.

<figref idref="DRAWINGS">FIG. 3</figref> is a more detailed view of the channel encoding process for the second group of users <b>210</b>. This second group <b>210</b>, for example, includes wireless data users that encode signals according to a format optimized for data transmission.

The individual channels are identified by modulating the input data by a pseudorandom noise (PN) code sequence that is the same code sequence used for the first group of users <b>110</b>. However, as will be understood shortly, the channels in the second group <b>210</b> are uniquely identified by specific orthogonal codes such as Walsh codes. Specifically, the channel encoding process for this second group of users <b>210</b> takes an input digital signal <b>402</b> and applies a number of codes as generated by a short code generator <b>405</b>, Walsh code generator <b>413</b>, and long code generator <b>407</b>.

As a first step, a quadrature modulator <b>404</b> provides an in-phase (i) and quadrature (q) signal path to a first pair of multipliers <b>406</b>-<i>i </i>and <b>406</b>-<i>q</i>. The short pseudorandom noise (PN) code generator <b>405</b> provides a short, in this case, a 215 length code used for spectrum spreading purposes. This short code therefore is the same as the short PN code used for each of the channels in the first group <b>110</b>.

A second step in the process is to apply an orthogonal code such as generated by the Walsh code generator <b>413</b>. This is accomplished by the multipliers <b>412</b>-<i>i </i>and <b>412</b>-<i>q </i>impressing the orthogonal code on each of the in-phase and quadrature signal paths. The orthogonal code assigned to each logical channel is different, and uniquely identifies such channels.

In a final step of the process, a second pseudorandom noise (PN) long code is applied to the (i) and (q) signal paths. The long code generator <b>407</b> thus forwards the long code to a respective one of the in-phase <b>408</b>-<i>i </i>and quadrature <b>408</b>-<i>q </i>multipliers. This long code does not uniquely identify each user in the second group <b>210</b>. Specifically, this code may be one of the very same long codes that are used in the first group that uniquely identify their first group of users <b>110</b>. Thus, for example, it is applied in the same manner as a short code chipping rate code so that one bit of the long code is applied to each bit output by the short code modulation process. In this manner, all of the users in the second group <b>210</b> appears as a single legacy user of the first group <b>110</b>. However, the users of the second group <b>210</b> may be uniquely identified given that they have been assigned unique orthogonal Walsh codes.

As the implementation in the preferred embodiment is on a reverse link <b>50</b>, additional information must be provided in order to maintain orthogonality among the various users in the second group <b>210</b>. Specifically, a maintenance channel <b>243</b> is therefore included in the forward link <b>40</b>. This maintenance or “heartbeat” channel provides synchronization information and/or other timing signals so that the remote units <b>214</b> may synchronize their transmissions appropriately. The maintenance channel may be time slotted. For more details of the formatting of this forward link maintenance channel <b>243</b>, reference can be made to a co-pending U.S. patent application Ser. No. 09/775,305 filed Feb. 1, 2001 entitled “MAINTENANCE LINK USING ACTIVE/STANDBY REQUEST CHANNELS,” which is hereby incorporated by reference in its entirety.

It should be understood that certain infrastructure may therefore be shared by both the second group of users <b>210</b> and first group of users <b>110</b>. For example, the antennas <b>218</b> and <b>118</b> although shown as separate base station antennas in <figref idref="DRAWINGS">FIG. 1</figref> may indeed be a shared antenna. Likewise, the location for the antennas may therefore be the same. This permits the second group of users <b>210</b> to share equipment and physical build-out locations already in place and in use by the legacy users <b>110</b>. This greatly simplifies the deployment of wireless infrastructure for this new group of users <b>210</b>, for example, new locations and new antenna sites need not be built out.

<figref idref="DRAWINGS">FIG. 4</figref> is a network diagram similar to <figref idref="DRAWINGS">FIG. 1</figref>. In this wireless network <b>400</b>, a first Base Station Processor (BSP) <b>220</b>-<b>1</b> and second base station processor <b>220</b>-<b>2</b> (collectively <b>220</b>) provide access to other networks (e.g., the Internet or PSTN) for access terminals <b>213</b>-<b>1</b>, <b>213</b>-<b>2</b>, . . . , <b>213</b>-<b>3</b> and handheld units <b>113</b>-<b>1</b>, <b>113</b>-<b>2</b>, and <b>113</b>-<b>3</b>. The base station processors <b>220</b> also support soft handoff of CDMA reverse links using orthogonal channels for non-legacy access terminals <b>213</b> while at the same time allowing legacy handheld units <b>113</b> to use reverse links in a typical manner. Access terminals <b>213</b> and handheld units <b>113</b> are interchangeably referred to as field units or Subscriber Access Units (SAUs).

“Legacy” field units refers to field units that are not equipped with a modulation process that applies unique orthogonal codes for sharing a common reverse link channel with other field units. “Non-legacy” field units refers to field units that are equipped with a modulation process that applies unique orthogonal codes for sharing a common reverse link channel with other field units. The BSPs <b>220</b> support soft handoff by selectively re-assigning timing control of reverse link channels based on criteria. In a preferred embodiment, both BSPs <b>220</b> provide power control feedback to the field units.

Continuing to refer to <figref idref="DRAWINGS">FIG. 4</figref>, above the antenna towers <b>218</b> are first and second timing diagrams <b>403</b>-<b>1</b> and <b>403</b>-<b>2</b> (collectively <b>403</b>) that illustrate the related timings of reverse link signals for each of the field units communicating with the respective base station processors <b>220</b>. These timing diagrams <b>403</b> illustrate a distinction between orthogonal reverse link channels that are time aligned and orthogonal or non-orthogonal channels that are not time aligned. As discussed above, each non-legacy access terminals <b>213</b> that shares a common reverse link channel has an additional coding process to add a unique orthogonal code to distinguish its reverse link signals from reverse link signals of other network devices using the common reverse link channel.

For purposes of this discussion, it is assumed that (i) the access terminals <b>213</b> share a common reverse link orthogonal channel and (ii) the three handheld units <b>113</b> use legacy, non-orthogonal, communication techniques in the reverse link.

In the first timing diagram <b>403</b>-<b>1</b>, the first base station processor <b>220</b>-<b>1</b> employs an alignment controller (not shown) to align the timing of reverse link orthogonal channels of access terminals for which the BSP <b>220</b>-<b>1</b> controls. In this case, the BSP <b>220</b>-<b>1</b> controls the timing of the reverse link logical channels <b>420</b>-<b>1</b> and <b>420</b>-<b>2</b>, represented by vertical tick marks <b>425</b>-<b>1</b> and <b>425</b>-<b>2</b>, of the first and second field units <b>213</b>-<b>1</b> and <b>213</b>-<b>2</b>, respectively. Reverse link channels that have their reverse links time aligned (i.e., common long codes phase aligned) are referred to as “native” orthogonal channels <b>410</b>. The third access terminal <b>213</b>-<b>3</b> that is also in communication with the first base station processor <b>220</b>-<b>1</b> does not have its reverse link logical channel <b>420</b>-<b>3</b> (<b>425</b>-<b>3</b>) time aligned with the reverse link logical channels of the first and second access terminals <b>213</b>-<b>1</b> and <b>213</b>-<b>2</b>. The third access terminal <b>213</b>-<b>3</b> has its reverse link channel <b>420</b>-<b>3</b> controlled by the second BSP <b>220</b>-<b>2</b>. Accordingly, the timing of the reverse link logical channel <b>420</b>-<b>3</b> (<b>425</b>-<b>3</b>) for the third field unit <b>213</b>-<b>3</b> is shown offset in the first timing diagram <b>403</b>-<b>1</b> from the native orthogonal channels <b>425</b>-<b>1</b> and <b>425</b>-<b>2</b>.

In the second timing diagram <b>403</b>-<b>2</b>, reverse link logical channels <b>420</b>-<b>1</b>, <b>420</b>-<b>3</b>, <b>420</b>-<b>4</b>, <b>420</b>-<b>5</b>, and <b>420</b>-<b>6</b> of the five wireless network devices <b>213</b>-<b>1</b>, <b>213</b>-<b>3</b>, <b>113</b>-<b>1</b>, <b>113</b>-<b>2</b>, and <b>113</b>-<b>3</b> in communication with the second base station processor <b>220</b>-<b>2</b> are represented by vertical tick marks <b>425</b>-<b>1</b>, <b>425</b>-<b>3</b>, <b>425</b>-<b>4</b>, <b>425</b>-<b>5</b>, and <b>425</b>-<b>6</b>, respectively. The second BSP <b>220</b>-<b>2</b> controls the timing of the third access terminal <b>213</b>-<b>3</b> reverse orthogonal link <b>420</b>-<b>3</b> (<b>425</b>-<b>3</b>) but neither of the other access terminals <b>213</b>-<b>1</b>, <b>213</b>-<b>2</b>. Therefore, as expected, the reverse link logical channels <b>420</b> (<b>425</b>) are offset in phase from one another at the second BSP <b>220</b>-<b>2</b>, as indicted in the second timing diagram <b>403</b>-<b>2</b>. Three of the reverse link channels <b>425</b>-<b>1</b>, <b>425</b>-<b>5</b>, and <b>425</b>-<b>6</b> are relatively close together in time at the second BSP <b>220</b>-<b>2</b> and are referred to as “foreign” orthogonal channels <b>415</b>.

The foreign orthogonal channels <b>415</b> are not truly orthogonal in that the channels do not have the unique orthogonal codes to distinguish one from another on a common, reverse link channel. Therefore, if the foreign orthogonal channels <b>415</b> were to be aligned, they would destructively interfere with each other at the second BSP <b>220</b>-<b>2</b>. In a particular situation, each of the base station processors <b>220</b> may be supporting native orthogonal channels <b>410</b> and foreign or non-orthogonal channels <b>415</b>. This situation indicates that a combination of non-legacy and legacy field units, respectively, can be used within the same cell zone.

In existing orthogonal technology, there is no soft handoff technique in the reverse link for when a field unit, such as one of the access terminals (e.g., <b>213</b>-<b>3</b>), moves from a cell zone of a first base station processor <b>220</b>-<b>1</b> to a cell zone of a second base station processor <b>220</b>-<b>2</b>. The reverse link soft handoff technique disclosed herein (i) supports communication in the reverse link from non-legacy wireless network devices <b>213</b> to multiple base station processors <b>220</b>, (ii) performs timing and power control (described later), and (iii) coordinates which of the multiple base station processors <b>220</b> is the “master” of the reverse link timing control for a field unit based on criteria, described in reference to <figref idref="DRAWINGS">FIG. 8</figref>. By coordinating which of the multiple BSPs <b>220</b> controls timing of the reverse link channel of a given access terminal <b>213</b>, the given access terminal <b>213</b> can move from one cell zone to another cell zone without loss of connection in the reverse link. The principles of the present invention also include a technique for rapid orthogonal timing alignment (i.e., adjusting the phase of the long code of the common logical channel for an access terminal <b>213</b> such that the common reverse link channel is time aligned, or mutually orthogonal, with the common reverse link channel of other access terminals <b>213</b>).

The base station processor <b>220</b> receiving control of the timing of the reverse link channel determines a gross offset of the timing of the field unit's reverse link logical channel as a function of the timing of the reverse link logical channel of other field units sharing the same reverse link logical channel. The gross offset is transmitted to the field unit <b>213</b> in the form of an offset command or offset message. Based on the gross offset information, the field unit makes a coarse timing adjustment of the logical channel in accordance with the gross timing offset. Following the coarse timing adjustment, a fine timing adjustment may be made in accordance with fine timing offsets that may be measured by the base station processor <b>220</b> following the coarse timing adjustment of the reverse link logical channel <b>420</b>.

<figref idref="DRAWINGS">FIG. 5</figref> is a block diagram of one of the base station processors <b>220</b>-<b>1</b> that includes provisions for soft handoff of a CDMA reverse link utilizing an orthogonal channel structure. The base station processor <b>220</b>-<b>1</b> receives reverse link channels from the field units <b>113</b>, <b>213</b> via the antenna tower <b>218</b>. A receiver <b>505</b> receiving a reverse link channel from a given field unit <b>213</b> sends the received signal to an orthogonal timing controller <b>510</b>. The orthogonal timing controller <b>510</b>, or equivalent unit, determines a gross timing offset <b>513</b> with respect to reverse link channels from other field units sharing the same reverse link logical channel. The gross timing offset <b>513</b> may be an absolute measure for transmittal to the given field unit <b>213</b> in the form of a command or may be a relative measure and sent back to the given field unit <b>213</b> in the form of a message, with the given field unit <b>213</b> using additional processing to determine the timing offset (i.e., phase adjustment) of the reverse link signal. A combination of absolute and relative measures may also be employed.

<figref idref="DRAWINGS">FIG. 6A</figref> is a schematic diagram of the network having the first base station processor <b>220</b>-<b>1</b> and second base station processor <b>220</b>-<b>2</b>. The base station processors <b>220</b> include respective alignment controllers <b>515</b>. The alignment controllers <b>515</b> are used by the base station processors <b>220</b> to select or control which base station processor <b>220</b> controls the timing alignment of the reverse links <b>420</b> of the field units <b>213</b>.

To determine which BSP <b>220</b> should control the timing alignment for the field unit <b>213</b>-<b>1</b>, the alignment controllers <b>515</b> may calculate a metric (e.g., Signal-to-Noise ratio (SNR)) associated with the signal received from the field unit <b>213</b>-<b>1</b>.

A given alignment controller <b>515</b> may issue a message to other alignment controller(s) <b>515</b> to tell the other base station processors <b>220</b> that the associated base station processor <b>220</b> associated with the given alignment controller <b>515</b> is going to control the timing of the reverse link channel of the field unit <b>213</b>-<b>1</b>. Alternatively, the given alignment controller <b>515</b> may issue a command or message to another alignment controller <b>515</b>, such as the alignment controller <b>515</b> in the second base station processor <b>220</b>-<b>2</b>, that the second base station processor <b>220</b>-<b>2</b> should control the timing of the reverse link channel of the field unit <b>213</b>-<b>1</b>. Other negotiating arrangements may occur between or among the alignment controllers <b>515</b> to determine which base station processor <b>220</b> is going to control the alignment of the field unit <b>213</b>. Once a base station processor <b>220</b> has been commanded or has elected to control the timing of the orthogonal reverse link channel, the orthogonal timing controllers <b>510</b> are employed to determine a gross timing offset, as discussed above for facilitating the timing control handoff.

<figref idref="DRAWINGS">FIG. 6B</figref> is a schematic diagram of the wireless network in which the alignment controller <b>515</b> is deployed as part of the field unit <b>213</b>-<b>1</b>, in this case incorporated into the subscriber access unit <b>214</b>-<b>1</b>. Alternatively, the alignment controller <b>515</b> may be included in the PC <b>212</b>-<b>1</b> or as a standalone unit electrically connected to either the Subscriber Access Unit (SAU) <b>214</b>-<b>1</b> or PC <b>212</b>-<b>1</b>.

In this arrangement, the alignment controller <b>515</b> provides a command or message to the SAU <b>214</b>-<b>1</b> at the field unit <b>213</b>-<b>1</b> to cause the field unit <b>213</b>-<b>1</b> to respond to a timing control signal received from either the first base station processor <b>220</b>-<b>1</b> or second base station processor <b>220</b>-<b>2</b>.

<figref idref="DRAWINGS">FIG. 6C</figref> is a schematic diagram of the wireless network <b>400</b> in which the alignment controller <b>515</b> is deployed in the base station controller (<b>123</b>). In this case, the alignment controller <b>515</b> may receive information from each of the orthogonal timing controllers <b>510</b> from the first base station <b>220</b>-<b>1</b> or the second base station <b>220</b>-<b>2</b> to determine which base station processor <b>220</b> should be controlling the timing of the orthogonal, reverse link channel for the field unit <b>213</b>-<b>1</b>. The alignment controller <b>515</b> may make this determination based on a number of factors, such as the signal-to-noise ratio of the reverse link signal at each of the base station processors <b>220</b>. The alignment controller <b>515</b> may use commands or messages to indicate which base station processor <b>220</b> is to control the timing of the reverse link of the field unit <b>213</b>-<b>1</b>. In either case, the selected base station processor <b>220</b> may issue a command or message to the field unit <b>213</b>-<b>1</b> that it is the base station processor <b>220</b> that will be controlling the timing of the orthogonal reverse link channel. It should be understood that the alignment controller <b>515</b> may also understand the concept of diversity and make selections as to which base station processor <b>220</b> is to control the timing of the reverse link channel so as to maximize the effectiveness of diversity between the base station processors <b>220</b>.

<figref idref="DRAWINGS">FIG. 7</figref> is a flow diagram of a soft handoff process of a CDMA orthogonal reverse link in accordance with the principles of the present invention. In this example, the first base station processor <b>220</b>-<b>1</b> executes a first process <b>700</b>, and the access terminal <b>213</b> executes a second process <b>735</b>. Following the start of the BSP process <b>700</b> in step <b>705</b>, the BSP process <b>700</b> waits to receive a reverse link signal in step <b>710</b> from the access terminal <b>213</b>. Following the start of the access terminal process <b>735</b> in step <b>740</b>, the access terminal <b>213</b>, in step <b>745</b>, transmits a reverse link signal with the unique orthogonal code on a reverse link channel common to reverse link signals of other access terminals <b>213</b>. The BSP process <b>700</b> receives the reverse link signal in step <b>710</b> and continues in step <b>715</b>. In step <b>715</b>, the BSP process <b>700</b> determines whether the long code, identifying the access terminal <b>213</b> belonging to an orthogonal reverse link group, in the reverse link signal is in phase with long codes of other access terminals <b>213</b> in the same access terminal group, as described in reference to <figref idref="DRAWINGS">FIGS. 2 and 3</figref>. It is the long codes, and not the unique, specific, orthogonal codes, such as Walsh codes, that are time aligned by the base station processor <b>700</b>. The unique, identifying codes of the reverse link signals are mutually orthogonal when the long codes are phase.

If the long code in the reverse link signal is in phase (i.e., time aligned) with the long codes of other reverse link signals of other access terminals <b>213</b> in the same mutually orthogonal reverse link group, the process <b>700</b> ends at step <b>730</b>. If the long code is not in phase with long codes in reverse link signals of other access terminals, the BSP process <b>700</b> continues in step <b>720</b>, where a determination of the gross timing offset is made by the orthogonal timing controller <b>510</b>, as discussed above in reference to <figref idref="DRAWINGS">FIG. 5</figref>.

The BSP process <b>700</b> continues in step <b>725</b>, where the base station processor <b>220</b> transmits the gross timing offset to the access terminal <b>213</b> in the form of a command or message. The access terminal process <b>735</b> receives the gross timing offset and adjusts the timing of the reverse link signal in step <b>750</b>. The access terminal process <b>735</b> ends in step <b>755</b>, and the BSP process <b>700</b> ends in step <b>730</b>.

<figref idref="DRAWINGS">FIG. 8</figref> is a flow diagram of the two base station processors <b>220</b>-<b>1</b> and <b>220</b>-<b>2</b> as they interact with the access terminal <b>213</b>. The first base base station processor <b>220</b>-<b>1</b> executes a process <b>800</b> that controls the timing of the reverse link of the access terminal <b>213</b>. The other base station processor <b>220</b>-<b>2</b> executes a process <b>802</b> that provides processing that is not controlling the timing of the reverse link of the access terminal <b>213</b>. The access terminal <b>213</b> executes its own process <b>833</b>. The process <b>833</b> is capable of receiving feedback, making adjustments to the timing of the reverse link signal in coarse and fine amounts, and making power level adjustments in accordance with power level feedback received from the base station processors <b>220</b>.

The access terminal <b>213</b> transmits signals (step <b>836</b>) that are received by the first base station processor <b>220</b>-<b>1</b> and the second base station processor <b>220</b>-<b>2</b>. In this example, it is assumed that the first base station processor <b>220</b>-<b>1</b> has previously been selected to control the timing of the reverse link signal by the access terminal <b>213</b>. The first base station processor <b>220</b>-<b>1</b> thus receives the reverse link orthogonal signals (step <b>803</b>) from the access terminal <b>213</b> that is either aligned with other reverse link signals sharing the same reverse link channel or is to be aligned with other reverse link signals from other access terminals <b>213</b> using the same reverse link channel. The base station processor <b>220</b>-<b>1</b> determines whether the signal from the access terminal <b>213</b> meets a timing criterion or criteria in step <b>806</b>. If the signal does not meet a timing criterion or criteria, the process <b>800</b> determines a gross timing offset to feed back to the access terminal <b>213</b> to bring the signal in alignment with the other signals using the same code. Feedback is received by the access terminal <b>213</b> in step <b>839</b>. If the signal meets the timing criterion or criteria, the process <b>800</b> continues in step <b>809</b>, where the process <b>800</b> determines whether a fine timing offset is necessary. If yes, the process <b>800</b> sends to the access terminal <b>213</b>, which is the fine timing offset, which is received in step <b>839</b> of the process <b>833</b> executed by the access terminal <b>213</b>. If no fine timing offset is necessary, the process <b>800</b> continues in step <b>815</b>.

In step <b>815</b>, the base station processor <b>220</b>-<b>1</b> determines whether the power level of the signal transmitted by the access terminal <b>213</b> should be adjusted. Similarly, the second base station processor <b>220</b>-<b>2</b> also determines whether it should cause a power level adjustment in step <b>815</b> of the access terminal <b>213</b>. In either case, the power level offsets are sent to the access terminal <b>213</b> in the forward link.

If no power level adjustment is needed, in reference to both the first base station processor process <b>800</b> and second base station processor process <b>802</b>, the respective processes continue to step <b>818</b>, where a determination is made as to whether timing control handoff should be initiated. Timing control handoff may be initiated based on a set of criteria: <ul id="ul0003" list-style="none"><li id="ul0003-0001" num="0000"><ul id="ul0004" list-style="none"><li id="ul0004-0001" num="0096">(a) the metric of an alternative path exceeds a threshold for a predesignated period of time;</li><li id="ul0004-0002" num="0097">(b) the metric of an alternative path exceeds a threshold relative to the current path for a designated period of time;</li><li id="ul0004-0003" num="0098">(c) the currently selected path drops below an absolute metric; and</li><li id="ul0004-0004" num="0099">(d) the candidate path exceeds an absolute metric, where the metric may be one or more of the following: <ul id="ul0005" list-style="none"><li id="ul0005-0001" num="0100">(a) power;</li><li id="ul0005-0002" num="0101">(b) SNR;</li><li id="ul0005-0003" num="0102">(c) variance of the power;</li><li id="ul0005-0004" num="0103">(d) variance of the SNR; and</li><li id="ul0005-0005" num="0104">(e) relative ratio of the two paths.</li></ul></li></ul></li></ul>

If there has been an initiation of timing control handoff, then, in step <b>821</b>, the base station processor <b>220</b>-<b>1</b> updates other base station processors and the base station controller <b>123</b>. The access terminal <b>213</b> may also be told of the timing control handoff. If the timing control has not been handed off, the processes <b>800</b> and <b>802</b> continue in step <b>824</b>, where a determination is made to release or accept the timing control should another base station processor <b>220</b>, base station controller <b>123</b>, or access terminal <b>213</b> send a command or message to the base station processor <b>220</b> that it will be controlling the timing of the reverse link signal. If the base station processor releases or accepts timing control duties, the processes <b>800</b>, <b>802</b> continue in step <b>830</b> to update system operating parameters; otherwise, the processes <b>800</b>, <b>802</b> continue back to step <b>803</b> to receive signals from the access terminals <b>213</b>.

The process <b>833</b> executed by the access terminal <b>213</b> receives feedback in step <b>839</b> and processes the feedback as follows. First, if no feedback is received, the process <b>833</b>, in this embodiment, loops waiting for feedback in step <b>839</b>. If feedback is received, the process continues in step <b>842</b> to determine whether a coarse timing adjustment command or message has been received. If yes, the coarse timing adjustment is made in step <b>845</b>. It should be understood that the course timing adjustment may be an absolute or relative measure, as disclosed above.

In step <b>848</b>, the access terminal <b>213</b> determines whether a fine timing adjustment command or message has been received. If yes, the fine timing adjustment is made in step <b>851</b>. It should be understood that the fine timing adjustment is typically a differential command or message. Following the fine timing adjustment, the process <b>833</b> determines whether a power level adjustment command or message has been received. If yes, the access terminal <b>213</b> adjusts the power level in step <b>857</b>.

Following the adjustments to the timing or power, the process <b>833</b> updates the operating parameters of the access terminal <b>213</b> in step <b>860</b>. Following update of the system parameters, the process <b>833</b> repeats at step <b>839</b>, awaiting feedback from one or more base station processors <b>220</b>.

<figref idref="DRAWINGS">FIG. 9</figref> is a flow diagram of processes <b>900</b>, <b>920</b> executed by the base station processors <b>220</b> and the access terminal <b>213</b>, respectively, for adjusting the power level of the reverse link signal transmitted by the access terminal <b>213</b>. Referring to the processes <b>900</b> executed by the base station processors <b>220</b>, the processes <b>900</b> begin in step <b>905</b>. In step <b>910</b>, the base station processors <b>220</b> determine whether to cause the access terminal <b>213</b> to change the power level of the reverse link signal in step <b>910</b>. If the change of the reverse link signal power level is desired, feedback is sent to the access terminal <b>213</b> in the form of a command or message. The base station processor <b>220</b> process <b>900</b> ends in step <b>915</b>.

The process <b>920</b> executed by the access terminal <b>213</b> begins in step <b>925</b>. Once feedback is received in step <b>930</b>, the process <b>920</b> continues in step <b>935</b>, where a determination is made as to whether all base station processors <b>220</b> are requesting a power level increase. If yes, the process <b>920</b> continues in step <b>940</b>, where the access terminal <b>213</b> increases the power level of the reverse link signal as much as the lowest increase feedback. If not all of the base station processors <b>220</b> are requesting power level increase, a determination is made in step <b>945</b> as to whether any base station processor <b>220</b> is requesting a power level decrease. If yes, the access terminal <b>213</b>, in step <b>950</b>, decreases a power level as much as a lowest decrease feedback. The process <b>920</b> ends in step <b>955</b> or may simply loop back to step <b>930</b> to wait to receive a power level feedback.

While power control is being maintained to both the orthogonal and non-orthogonal base stations, commands or metrics may be sent to the subscriber base transmitter (i.e., access terminal <b>213</b>) via a forward link. The power control commands from each base station processor <b>220</b> may be based upon whether a signal quality metric is achieved at each respective base station processor <b>220</b>. This signal quality metric may be a bit-error-rate (BER), signal-to-noise ratio (SNR), received power, or Ec/Io, for example. Provided the metric is satisfied, a command to reduce transmission power may be sent. Since the access terminal <b>213</b> receives commands or messages from both base station processors <b>220</b>, often it reflects conflicting commands. When this occurs, the access terminal <b>213</b> obeys the command to “power down.” This is effectively an exclusive-OR function; for instance, a “power up” occurs if both base station processor <b>220</b> command power up. If either base station processor <b>220</b> commands a power down, a power down occurs. This holds true for multi-bit commands as well, where the minimum increase or the maximum decrease in power is obeyed.

While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.